Williams, 40, and American television actress Field, 35, are already parents to two-year-old Theodora Rose. While most celebrity couples try their hardest to keep personal moments like these private, the Take That star did exactly the opposite.
Robbie provided a live commentary of the birth by tweeting and sharing videos on his YouTube page from the hospital room. Yes, really.
"Erm, so, he's here. It's ten past three on what day? Monday? And we've been up way over 24 hours," Robbie says. "I've never been more in love and I've never been more proud of my wife, she's been absolutely astonishing."
He adds, "Er baby bud isn't having a name yet, we're still figuring it out. He's 8lb1oz." (Ayda quickly replies, "two ounces babe, every ounce counts.")
Of course, it wasn't the only video Robbie shared during his son's birth.
He also sang and danced along to his own song 'Candy' before giving a rendition of Frozen's 'Let It Go,' while Ayda was mid-labour.
It's worth a watch.
The proud dad let everyone know Ayda had gone into labour with this first tweet from the hospital early on Monday morning.
When Ayda goes into labour she comes correct ; ) RW x pic.twitter.com/BjikS91e3s
- Robbie Williams (@robbiewilliams) October 27, 2014
Those shoes? Amazing.
Congratulations to Robbie and Ayda! More celebrity baby bumps below: